The present invention relates to a method for determining the wear to a storage battery by monitoring the state of charge of the storage battery. The invention also relates to a monitoring device and a computer program for carrying out such a method.
As the life of batteries (e.g., rechargeable storage batteries or electrochemical energy stores) increases, wear occurs. In particular, wear occurs during discharging and charging of the batteries. In addition to discharging and charging, there are also operating conditions which accelerate the wear. These include, for example, the total operating life for a lead-acid rechargeable battery, which is the total time that has passed since it was first used, including those periods in which the rechargeable battery had no electrical load applied to it.
Furthermore, increased temperatures can exacerbate the wear during the periods when no electrical load is applied, and can exacerbate the wear caused by cyclic discharging and charging.
For use of storage batteries, it is desirable to determine the wear on the basis of the loss of storage capacity. However, in this case, the complexity of the processes that take place in a storage battery represents a problem which can be described only with difficulty using scientific methods.
By way of example, DE 195 40 827 C2 discloses an empirical method for determining the state of aging of a storage battery, in which a battery-specific family of characteristics is predetermined for battery aging. A battery aging value is determined with the aid of the family of characteristics, by detection of instantaneous values of the battery aging influencing variables for the storage battery being monitored.
DE 39 01 680 C3 discloses a method for monitoring the cold starting capability of a starter battery, in which the charge voltage is continuously observed when the internal combustion engine is running, and is monitored for exceeding or undershooting predetermined limit values. This makes it possible to identify a generator defect. Furthermore, the time profile of the voltage drop at the connecting terminals of the electrical starter is observed and evaluated during the starting process. However, it is difficult to characterize the available storage capacity of the storage battery using such a method.
DE 38 08 559 C2 discloses a method for monitoring the power limit of a starter battery, in which an amount of charge balance is produced by adding up the amounts of charge which have flowed into and out of the battery. The state of charge of the starter battery is assessed from this, in conjunction with the monitoring of a limiting terminal voltage and the temperature. It is also difficult to characterize the remaining maximum storage capacity of the battery in this case.
DE 101 58 029 A1 discloses a method for calculating a dynamic state of charge of a storage battery, in which correction factors are taken into account for various operating conditions relating to the current, temperature, and state of charge. Test cycles are carried out in which the storage battery is completely discharged. The number of test cycles and the average decrease in capacity per discharge cycle are determined and used to calculate a state of charge value. The capacity of the storage battery is increased by discharging it completely.
It would thus be advantageous to provide a method for determining the wear to a battery by monitoring the state of charge of the battery, by means of which a wear variable can be calculated by relatively reliable and simple means as a measure of the loss of storage capacity. It would also be advantageous to provide a monitoring device for use with a battery for determining the wear of the battery. It would also be advantageous to provide a system such as a computer program for determining the wear of the battery.
It would be advantageous to provide a method or system or the like of a type disclosed in the present application that provides any one or more of these or other advantageous features.